Exogenous gangliosides enhance recovery from cns injury

Establishment of a targeted analysis method for gangliosides in mouse tissues by HILIC-ESI-MS/MS

Gangliosides play an imperative role in cell signaling, neuronal recovery, apoptosis, and other physiological processes. For example, GM3 can regulate hypothalamic leptin resistance and control energy homeostasis, GD3 can mediate cell proliferation and differentiation and induce apoptosis, and GQ1b can stimulate neurogenesis. Therefore, the present study sought to establish and optimize the targeted analysis method for ganglioside subclasses and their molecular species using hydrophilic interaction liquid chromatography-triple quadrupole-MS/MS (HILIC-QQQ-MS/MS). Additionally, the fragmentation pattern of different ganglioside subclasses and their retention time patterns were analyzed, providing more accurate qualitative results. The limit of quantitation (LOQ) was as low as 10-4 ng. Moreover, the molecular species of gangliosides in the liver, cortex, and hypothalamus of C57BL/6 mice were analyzed using the established method. A total of 23 ganglioside subclasses with 164 molecular species, including 40 O-acetylated ganglioside molecular species and 28 NeuGc ganglioside molecular species, were identified using the semi-quantitative analysis method of an external standard curve corrected by an internal standard. In addition to NeuGc gangliosides, the contents of ganglioside subclasses were more abundant in the mouse brain than those in the mouse liver; especially, the contents of unsaturated gangliosides in the hypothalamus were much higher than those in the liver. Among them, O-acetylated gangliosides were detected only in the cortex and hypothalamus at a concentration of up to 100 μg/mg protein (40 molecular species). Overall, the proposed method expanded the detectable number of ganglioside subclasses and molecular species in biological samples and provided more opportunities for further study of the biological functions of gangliosides.

Impaired hypoglossal nerve regeneration in mutant mice lacking complex gangliosides: down-regulation of neurotrophic factors and receptors as possible mechanisms

Gangliosides, sialic acid-containing glycosphingolipids, have been considered to play roles as neurotrophic factors. Exogenous gangliosides added to the culture medium of neuronal cells or injected in artificially injured sites of nerve tissues actually showed neurotrophic factor-like effects such as neurite extension and alleviation of nerve tissue deterioration. In this study, neuroregeneration in the mutant mice lacking complex gangliosides was examined. To determine whether the nervous system maintains regenerative activity in the long-term absence of complex gangliosides, we analyzed hypoglossal nerve regeneration after axotomy in the mutant mice of GM2/GD2 synthase. These mice exhibited marked impairment of regenerative activity both in the number of surviving neurons and in the number of peroxidase-positive neurons. Moreover, reduced levels of gene expression of neurotrophic factors and their receptors including CNTF, p75 NTR, TrkB, and others in hypoglossal neurons were observed in real-time reverse transcription-polymerase chain reaction combined with laser capture microdissection, suggesting that these molecules are, at least partly, involved in the regeneration of lesioned nerves and that their expression levels are precisely controlled in the presence of intact expression of complex gangliosides.

Current status of clinical trials for acute spinal cord injury

Acute spinal cord injury (ASCI) occurs as a result of physical disruption of spinal cord axons through the epicenter of injury leading to deficits in motor, sensory, and autonomic function. This is a debilitating neurological disorder common in young adults that often requires life-long therapy and rehabilitative care, placing a significant burden on our healthcare system. While no cure exists, research has identified various pharmacological compounds that specifically antagonize primary and secondary mechanisms contributing to the etiology of ASCI. Several compounds including methylprednisolone (MPSS), GM-1 ganglio-side, thyrotropin releasing hormone (TRH), nimodipine, and gacyclidine have been tested in prospective randomized clinical trials of ASCI. MPSS and GM-1 ganglioside have shown evidence of modest benefits. Clearly trials of improved neuroprotective agents are required. Promising potential therapies for ASCI include riluzole, minocycline, erythropoietin, and the fusogen polyethylene glycol, as well as mild hypothermia.

Beneficial effects of GM1 ganglioside on photochemically-induced microvascular injury in cerebral cortex and hypophysis in rat

Gangliosides, the glycophospholipids which are abundantly present in the central nervous system, have been shown to stimulate neuronal regeneration and counteract the deleterious effects of ischemia on cerebral neurons. The further elucidate the mechanism of action of gangliosides in cerebral ischemia, we investigated the influence of GM1 ganglioside in the model of photochemically-induced microvascular injury in rat brain. The animals were injected with rose Bengal and illuminated through cranium with halogen lamp. This treatment resulted in the development of microthrombi and alterations in endothelial cells in the microvessels. Administration of 20 mg/kg GM1 ganglioside, 1 h before the photochemical reaction, largely reduced subsequent microvascular damage. In conclusion, the GM1 ganglioside is able to prevent microvascular damage in the central nervous system.

Prevention of the death of the rat axotomized hypoglossal nerve and promotion of its regeneration by bovine brain gangliosides

We have examined the time course of the neuronal death and regeneration of rat axotomized hypoglossal nerve with various conditions of the nerve resection, and established a useful system to measure neurotrophic activities of bioactive substances. In this system, neuronal death can be evaluated by counting surviving neurons in the nucleus of hypoglossal neuron at the brain stem, and the degree of the regeneration can be measured by counting horseradish peroxidase-positive cells at the same region after injection of horseradish peroxidase into tongue. Using this system, the effects of brain gangliosides on rat hypoglossal nerve regeneration following 5 mm transection were examined. The addition of a ganglioside mixture from bovine brain as well as the autograft strongly prevented the death of neurons and promoted the regeneration of the lesioned nerve at 10 weeks after the operation. Further analyses on the dose effects and injection sites of gangliosides were performed. Although the mechanisms of the neurotrophic effects of the gangliosides are unknown, the therapeutic application of gangliosides for neuronal degeneration is a promising approach.

Expression cloning of rat cDNA encoding UDP-galactose:GD2 beta1,3-galactosyltransferase that determines the expression of GD1b/GM1/GA1

Using an anti-GD1b monoclonal antibody, expression cloning of a cDNA for the beta1,3-galactosyltransferase gene (EC 2.4.1.62) was performed. KF4C, mouse melanoma B16 transfected with polyoma T antigen gene, and GM2/GD2 synthase cDNA was used as a recipient cell line for the cDNA library transfection. A cDNA clone of GD3 synthase, pD3T-31 was co-transfected with a cDNA library prepared from rat brain RNA using the pcDNAI expression vector. The isolated cDNA clone pM1T-9 predicted a type II membrane protein with 4 amino acids of cytoplasmic domain, 21 amino acids of transmembrane region, and a large catalytic domain with 346 amino acids. Introduction of the cDNA clone into a mouse melanoma line B16 previously transfected with a GM2/GD2 synthase gene resulted in the neo-synthesis of GM1. Co-transfection of the cell line with pM1T-9 and a GD3 synthase cDNA resulted in the expression of GD1b as well as GM1. Moreover, introduction of pM1T-9 into L cell (lacking GM3 synthase), previously transfected with GM2/GD2 synthase gene, resulted in the definite expression of asialo-GM1. These results indicated that GD1b/GM1/GA1 synthases were identical, as previously suggested based on enzymological analysis. In Northern blots of the beta1, 3-galactosyltransferase gene with total RNA from various rat tissues, a 1.6-kilobase mRNA was strongly expressed in spleen, thymus, kidney, and testis. However, the expression level of the gene in the adult brain tissue was not especially high. On the other hand, this gene was expressed at high levels in the rat brain of embryonal day 12, and reached a peak at around birth, then fell to low level in the adult brain.

Pharmacological strategies in CNS trauma

Delayed biochemical changes play an important role in tissue damage resulting from traumatic injuries to the central nervous system. Identification of such 'secondary' injury factors has led to the development of various pharmacological strategies aimed at limiting this progressive tissue destruction. In this review, Alan Faden and Steven Salzman discuss the pharmacological approaches that have the most experimental support. These include corticosteroids, antioxidants and free-radical scavengers, modulators of arachidonate metabolism, gangliosides, monoamine modulators, opioid receptor antagonists, TRH and its analogs, NMDA receptor antagonists, Ca2+ channel antagonists and platelet-activating factor antagonists.

Ganglioside treatment: reduction of CNS injury and facilitation of functional recovery

Increased attention has focused on the use of brain gangliosides as a treatment for brain injury. This review traces the progression of in vitro and in vivo research which led to studies which have demonstrated that ganglioside treatment can facilitate recovery after CNS damage in animal models (for example, lesions, transections, hypoxia, ischemia). Hypotheses regarding the ability of gangliosides to stimulate neuronal plasticity, modulate trophic factors and reduce injury processes are presented.

Ganglioside-induced alterations in hippocampal cholinergic enzymes and Na,K-ATPase after fimbria-fornix transection

Previous biochemical findings suggest that exogenous gangliosides enhance cholinergic sprouting in the hippocampus after partial lesions of the septohippocampal pathway. To assess whether GM1 ganglioside accelerates the onset of this sprouting after complete lesions, we measured cholinergic enzymes and Na,K-ATPase activity in the hippocampus of rats with unilateral fimbria-fornix transection. At 14 and 18 days postlesion, histochemical staining showed that acetylcholinesterase (AChE) was almost completely eliminated in the hippocampus ipsilateral to the transection in untreated and GM1-treated rats. Biochemical assays confirmed that GM1 treatments did not increase AChE activity in the denervated hippocampus. Rather, there were significant reductions of AChE and choline acetyltransferase activities in the ipsilateral hippocampus relative to the contralateral value (P less than .001); and the reductions were greater in GM1-treated rats than in untreated controls (P less than .001). Na,K-ATPase activity in the ipsilateral hippocampus increased by 10.1% in GM1-treated rats, whereas it decreased by 21.7% in untreated controls (P less than .05). Since Na, K-ATPase is enriched in synaptic membranes, the increased activity of this enzyme may indicate that GM1 treatments stabilize surviving synaptic membranes and/or accelerate the onset of sprouting in the denervated hippocampus. The reductions in cholinergic enzymes, however, imply that the sprouting pathway must be noncholinergic.

Effects of fimbria-fornix transection and ganglioside treatments on histochemical staining for glucose-6-phosphate dehydrogenase in the lateral septum

The present study examined whether ganglioside treatments would affect an enzyme marker (glucose-6-phosphate dehydrogenase; G6PDH) of neural metabolism in an established model system (the hippocamposeptal projection) of deafferentation and sprouting. Rats were subjected to unilateral transections of the fimbria-fornix (FF) in order to (1) interrupt the hippocamposeptal projection, (2) deafferent the lateral septal nucleus (LSN) ipsilaterally, and (3) induce sprouting by the contralateral FF. In untreated rats which were killed at 2-4 days postlesion, histochemical staining for G6PDH was reduced by 35-40% in the deafferented LSN relative to the contralateral side. However, at 6-8 days (i.e., when sprouting begins), staining intensity returned toward contralateral values (i.e., recovered). This pattern of changes in G6PDH staining was not observed in the caudate nucleus adjacent to the LSN. In ganglioside-treated rats which were killed at 4 days, there was a significantly smaller reduction of G6PDH staining in the deafferented LSN (23%; P = .05). This effect was not observed in the LSN of treated rats killed at 2 days, nor in the caudate nucleus at either time point. The present data indicate that (1) FF transection results in a reduction and subsequent recovery of G6PDH staining in the deafferented LSN; and (2) ganglioside treatments may accelerate the onset of the recovery of G6PDH activity. We suggest that gangliosides' effect on G6PDH reflects an acute enhancement of biosynthetic events in deafferented neurons.

Gangliosides (GM1 and AGF2) reduce mortality due to ischemia: protection of membrane function

As evidenced by their ability to reduce cerebral edema, exogenous ganglioside administration exerts acute effects on CNS injury processes. We report here that ganglioside (GM1 or AGF2) treatment results in a 52% decrease in mortality 48 hours after the induction of ischemia in gerbils by permanent unilateral ligation of the common carotid artery. By comparing the occluded vs. nonoccluded sides of the brain (cortex and hippocampus) we found a significant loss of membrane Na, K-ATPase activity due to ischemia in control animals, but no such differences were found between the hemispheres of ganglioside-treated gerbils. We hypothesize that gangliosides may be "protecting" membrane function as indicated by these ATPase analyses, reducing local CNS damage at the time of injury (i.e., reduced cell loss, fiber degeneration, membrane failure). By acutely limiting the extent of CNS tissue damage, conditions may be optimized for any subsequent CNS regrowth and functional recovery.

Neuritogenic and metabolic effects of individual gangliosides and their interaction with nerve growth factor in cultures of neuroblastoma and pheochromocytoma

The 4 major ganglioside species, GM1, GD1a, GD1b and GT1b (200 micrograms/ml), were tested individually for the ability to stimulate neuronal trophic responses. The growth parameters measured were: morphologic changes, quantitated by computer-assisted morphometry of neurite length and number per soma, and metabolic changes, indicated by alterations in ornithine decarboxylase activity (ODC). In addition, the interaction of each ganglioside with nerve growth factor (NGF) was investigated with an NGF-responsive pheochromocytoma PC12 cell line and NGF-insensitive neuroblastoma Neuro-2a cultures. PC12 cells responded to gangliosides only in the presence of NGF (20 micrograms/ml): GM1 produced the greatest morphologic response, but did not alter metabolic levels; GT1b increased both parameters. The presence (5 micrograms/ml) or absence of NGF did not have an effect on the ganglioside-mediated morphologic responses of Neuro-2a cells to each species: GD1b elicited the greatest increase in neurite length, while GD1a and GT1b stimulated both length and number. In contrast, while GT1b alone was able to elevate ODC activity independently of NGF, the simultaneous exposure of Neuro-2a cultures to NGF and GM1 or GD1a resulted in a stimulation of cellular metabolism. These results indicate that each ganglioside species has a specific target action in the stimulation of different trophic responses and that performance in one category is not a predictor of the result in another. In addition, it is possible to confer a sensitivity to NGF by simultaneous treatment with specific gangliosides. This indicates that membrane gangliosides may modulate the actions of neurotrophic factors.

GM1 ganglioside counteracts selective neurotoxin-induced lesion of developing serotonin neurons in rat spinal cord

The effect of exogenous monosialoganglioside GM1 on neurotoxin-induced lesioning of bulbo-spinal serotonergic neurons of newborn rats was studied by means of biochemical and immunocytochemical techniques. 5,7-dihydroxytryptamine (5,7-HT, a selective serotonin neurotoxin) treatment of newborn rats caused a pronounced reduction of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in the thoracic and lumbar spinal cord, while an increase of 5-HT and 5-HIAA was found in the pons medulla. These biochemical alterations were regionally correlated with similar changes in 5-HT nerve terminal density analyzed by image analysis. GM1 administration (30 mg/kg for 4 consecutive days) antagonized the reduction of 5-HT and 5-HIAA levels induced by 5,7-HT treatment in the lumbar spinal cord of 2-month-old rats, as well as the decrease of 5-HT nerve terminal density in both thoracic and lumbar spinal cord of 1- and 2-month-old rats. A minor counteracting effect of GM1 was found in the pons medulla where the neurotoxin induced an increase of 5-HT and 5-HIAA levels. These data support the hypothesis that GM1 may have a preventing action on retrograde degenerative processes following chemical lesion and/or a growth-stimulating effect on injured 5-HT neurons.

Effects of ganglioside treatments on lesion-induced behavioral impairments and sprouting in the CNS

Recent findings suggest that exogenous gangliosides improve recovery of a learned behavior (alternation in a T-maze) which is thought to be related to sprouting after lesions of the entorhinal cortex. In the present investigation, we studied an unlearned behavior (the open-field hyperactivity resulting from bilateral entorhinal lesions) to evaluate whether ganglioside treatments reduce the severity of initial postlesion impairments or improve recovery. We also examined whether the treatments enhance the sprouting of septodenate fibers which parallels the recovery of open-field activity. The typical behavioral changes induced by bilateral entorhinal lesions include hyperactivity, reduced habituation of activity, and a gradual time-dependent return toward control levels. We found that rats treated with total brain gangliosides (30 mg/kg) showed a smaller lesion-induced increase, consistently lower levels, and greater within-session habituation of activity than did saline-treated counterparts. Control rats treated with gangliosides did not exhibit a reduction in activity, suggesting that the effect was on lesion-induced hyperactivity rather than on activity, per se. Ganglioside-treated rats showed a slight, but consistently smaller lesion-induced sprouting response by the septodentate pathway than did untreated counterparts at all postlesion intervals examined (3, 5, 7, and 10 days). The present findings indicate that ganglioside treatments reduce the severity of the initial behavioral effects after entorhinal lesions without enhancing the sprouting by septodentate fibers.

Reduction of cerebral edema with GM1 ganglioside

Administration of exogenous gangliosides has been reported to accelerate neurite outgrowth in vitro, and to enhance peripheral nerve regeneration and central nervous system recovery subsequent to damage. After injury, facilitation of CNS recovery with GM1 ganglioside treatment has been postulated to be due to enhanced neuronal regeneration. Since maximal recovery is achieved when experimental animals are treated before injury with GM1 ganglioside, an alternative or parallel mechanism is that gangliosides are "protecting" the CNS by limiting the extent of damage (ie, cell loss, process degeneration, membrane disruption). This may be due to a reduction in the edema subsequent to injury. In this study, rats were treated for 2 days with 20 mg/kg/day of GM1 ganglioside. On the third day they were subjected to a unilateral lesion (mechanical) of one cerebral hemisphere and given another 20 mg/kg of GM1. On the fourth day brains were removed for analysis of edema resulting from the injury. In treated animals there was a significant reduction in edema as measured either in the entire injured hemisphere (23%) or in the area of injury (33%). No effect was seen outside the damaged area. Since exogenous gangliosides can spontaneously "insert" into membranes, it is postulated that the effect of the GM1 may be due to alterations of membrane processes (eg, lipid hydrolysis, phospholipase activation, levels and membrane action of arachidonic acid, ionic permeation) that are characteristic of edema.